EuclidWas the train descending a significant grade? Have there been many instances of peeing away the air on relatively flat trackage? With the comments about a possible brake problem, what has been the underlying basis for that piece of information? Is it nothing more than one possible conclusion simply because the train did not stop?
With the comments about a possible brake problem, what has been the underlying basis for that piece of information? Is it nothing more than one possible conclusion simply because the train did not stop?
Grades don't have to be significant for 10 - 12 - 15 -18K tons or more to do horrendous damage when the train runs away. Grade and tonnage build momentun - momentum that takes increasingly more braking power to bring back under control.
That I am aware of, there has not been any published 'cause' for this incident.
NDG - Thanks for this link - not of this incident but illustrative
https://www.liveleak.com/view?t=sNzK_1539570515
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BaltACD Euclid Was the train descending a significant grade? Have there been many instances of peeing away the air on relatively flat trackage? With the comments about a possible brake problem, what has been the underlying basis for that piece of information? Is it nothing more than one possible conclusion simply because the train did not stop? Grades don't have to be significant for 10 - 12 - 15 -18K tons or more to do horrendous damage when the train runs away. Grade and tonnage build momentun - momentum that takes increasingly more braking power to bring back under control. That I am aware of, there has not been any published 'cause' for this incident.
Euclid Was the train descending a significant grade? Have there been many instances of peeing away the air on relatively flat trackage? With the comments about a possible brake problem, what has been the underlying basis for that piece of information? Is it nothing more than one possible conclusion simply because the train did not stop?
I realize that no cause has been published. I was just asking those who mentioned hearing of a possible braking problem if there was any reason given for suspecting a possible braking problem.
EuclidIs it nothing more than one possible conclusion simply because the train did not stop?
Give the man a cigar!
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
BaltACD NDG - Thanks for this link - not of this incident but illustrative https://www.liveleak.com/view?t=sNzK_1539570515
You are welcome!
Thank You.
EuclidI was just asking those who mentioned hearing of a possible braking problem if there was any reason given for suspecting a possible braking problem.
Think about who mentioned it.
Dave H. Painted side goes up. My website : wnbranch.com
It looks like the area where it happened is on a mostly 1.5 % grade. One report I was shown by a coworker said the train picked up cars (I think in Laramie WY) and was 12000 tons.
One of the engines involved was a SD70m, but unknown when I was shown this info last week was if it was leading. They have a mechanical brake valve, either a 26L or the desk top equivalent, and lately some have been having pressure maintaining issues. They can have other defects where they don't work properly, but as someone has observed - you always have the "big Hole" as a last resort. Assuming the brake pressure hasn't dropped below about 45 or 50 psi. Below that pressure, emergency may not be transmitted through the brake pipe. Passenger equipment will automatically dump when pressure drops below 20 psi as a fail safe last resort. Freight equipment doesn't have that feature.
Jeff
jeffhergert It looks like the area where it happened is on a mostly 1.5 % grade. One report I was shown by a coworker said the train picked up cars (I think in Laramie WY) and was 12000 tons. One of the engines involved was a SD70m, but unknown when I was shown this info last week was if it was leading. They have a mechanical brake valve, either a 26L or the desk top equivalent, and lately some have been having pressure maintaining issues. They can have other defects where they don't work properly, but as someone has observed - you always have the "big Hole" as a last resort. Assuming the brake pressure hasn't dropped below about 45 or 50 psi. Below that pressure, emergency may not be transmitted through the brake pipe. Passenger equipment will automatically dump when pressure drops below 20 psi as a fail safe last resort. Freight equipment doesn't have that feature. Jeff
Thanks Jeff. I can see how that would lead to questioning the brake response.
jeffhergert They can have other defects where they don't work properly, but as someone has observed - you always have the "big Hole" as a last resort.
I gradually opened a back-up hose once - to the point it was fully open and exhausting air from the brake line. Because I had done so gradually, the brakes never dumped, and there was now no way to make them do so.
tree68I gradually opened a back-up hose once - to the point it was fully open and exhausting air from the brake line. Because I had done so gradually, the brakes never dumped, and there was now no way to make them do so.
Used to do it all the time to cars attached to ground air.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
tree68 jeffhergert They can have other defects where they don't work properly, but as someone has observed - you always have the "Big Hole" as a last resort. I gradually opened a back-up hose once - to the point it was fully open and exhausting air from the brake line. Because I had done so gradually, the brakes never dumped, and there was now no way to make them do so.
jeffhergert They can have other defects where they don't work properly, but as someone has observed - you always have the "Big Hole" as a last resort.
So this is shaping up as an attended version of Lac Megantic...
OvermodSo this is shaping up as an attended version of Lac Megantic...
Probably better to say that this is one possibility among the many already discussed. Running a signal is likely the higher percentage choice.
SD70DudeHe may have been thinking of Trip Optimizer, which DOES operate the train, to varying degrees of success. TO is so good that it is not allowed to use the air brakes, and requires the Engineer to take over in numerous other situations too. But between TO and PTC the eventual goal is to run autonomous trains. A couple of Class I's have publicly stated that.
Yeah, that what I was referring to. Please pardon my D'oh moment.
Wouldn't say that at all. Lac Megantic was a failure to properly secure a standing train. While we don't know what the cause was, we know that it wasn't that. Completely different sets of rules and procedures and possible causes.
dehusmanWouldn't say that at all. Lac Megantic was a failure to properly secure a standing train. While we don't know what the cause was, we know that it wasn't that.
The similar proximate cause was, undeniably, the leaking off of the brake air, almost precisely at the sort of rate recounted in earlier posts in this thread, resulting in the automatic brake failing to apply and hold or slow the train when the independent no longer held it. Whether the leak was through a defective valve or an air turbine, or whether there were insufficient handbrakes applied to hold the train with the airbrakes released, are not particularly germane to this discussion.
There is one thing, though. Balt said
BaltACDImmediately, we have cast guilt on the following train's crew.
It seems to me that, regardless of a 'cause' releasing the air from the car reservoirs, there would have been an indication on the head-end air gauges. Is that an erroneous conclusion, and (if so) what combination of service faults or failures would produce normal-appearing gauge readings with substantially no application pressure available at the wheel cylinders?
I'll be interested to see what the NTSB says regarding the state of the brake system.
OvermodThe similar proximate cause was, undeniably, the leaking off of the brake air
The cause of the Lac Megantic crash was a failure to set sufficient handbrakes. The air brakes had nothing to do with the cause of the accident.
Plus we don't know if the air "leaked off". It could be insufficient supply, it could be too much was used, it could be a failure of the brake valve, it could be a lot of different things that have nothing to do with a leak. For example, if the engineer used the brakes too often without allowing them to recharge, that's not a "leak", that is an intentional use of the brakes.
There are things that point to an air brake problem, but we don't know any of the details about what the crew did and and what the train did.
FRA signal worker stated it was a runaway. DS notified other trains to stop and get off. That is all known to date.
Do the automatic brake valves on UP power have "freight" and "passenger" positions, or do you only have "in" and "out"?
In my experience changing the automatic mode from "freight" to "passenger" (with the automatic released of course) usually makes the unit pressure maintain properly. Nearly all of CN's units with 26 and 30 type brake valves (except the ex-Oakway SD60's) have all 3 positions.
We discussed this problem in another thread not so long ago, and I think it was Big Jim who said that a leaky gasket somewhere inside the control stand is the most common cause of that problem.
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Overmod tree68 jeffhergert They can have other defects where they don't work properly, but as someone has observed - you always have the "Big Hole" as a last resort. I gradually opened a back-up hose once - to the point it was fully open and exhausting air from the brake line. Because I had done so gradually, the brakes never dumped, and there was now no way to make them do so. So this is shaping up as an attended version of Lac Megantic...
The procedure they are describing is known as venting a train, and as long as the reduction rate exceeds 3 PSI per minute it will result in a full service brake application on the train, and a brake pipe pressure of 0 PSI.
The purpose of that procedure is to not put the train in emergency in order to save the air in the cars' emergency reservoirs, and to prevent emergency vent valves on the cars from sticking open (a real problem in cold weather).
At Lac-Megantic the auxiliary reservoir air leaked out through the brake pipe due to the very slow reduction rate and no air went to the cars' brake cylinders, which is the exact opposite result of the venting procedure Zug and Larry described.
Cycle braking too many times can indeed achieve the same end result as Lac-Megantic, but so far all we have here is rumours, no hard facts yet.
A unintentional release or blockage of the brake pipe could easily cause the same end result, if the Engineer did not catch it right away.
SD70DudeCycle braking too many times can indeed achieve the same end result as Lac-Megantic, but so far all we have here is rumours, no hard facts yet.
I believe a grade was mentioned, and that this was reported as a runaway. Cycle braking (and thus pssng away one's air) has been a factor in a number of runaways. Another possibility for the list.
SD70DudeThe procedure they are describing is known as venting a train, and as long as the reduction rate exceeds 3 PSI per minute it will result in a full service brake application on the train, and a brake pipe pressure of 0 PSI. The purpose of that procedure is to not put the train in emergency in order to save the air in the cars'
Did you mean to say, "as long as the reduction rate does not exceed 3 PSI per minute..."? My understanding of drawing off air slowly to avoid triggering an emergency application is that the rate of reduction has to be under a certain amount.
SD70DudeWe discussed this problem in another thread not so long ago, and I think it was Big Jim who said that a leaky gasket somewhere inside the control stand is the most common cause of that problem.
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BigJim SD70Dude We discussed this problem in another thread not so long ago, and I think it was Big Jim who said that a leaky gasket somewhere inside the control stand is the most common cause of that problem. What I think you are referring to is when I said that a small gasket on the back of the equalizing reservoir gauge, if damaged, can cause a leak on the equalizing reservoir side, so, that when the brake application is made, the pressure keeps leaking down on the equalizing reservoir causing the brakes to keep being applied relative to the amount of leakage.
SD70Dude We discussed this problem in another thread not so long ago, and I think it was Big Jim who said that a leaky gasket somewhere inside the control stand is the most common cause of that problem.
What I think you are referring to is when I said that a small gasket on the back of the equalizing reservoir gauge, if damaged, can cause a leak on the equalizing reservoir side, so, that when the brake application is made, the pressure keeps leaking down on the equalizing reservoir causing the brakes to keep being applied relative to the amount of leakage.
Yes that's what I was thinking of.
Euclid SD70Dude The procedure they are describing is known as venting a train, and as long as the reduction rate exceeds 3 PSI per minute it will result in a full service brake application on the train, and a brake pipe pressure of 0 PSI. The purpose of that procedure is to not put the train in emergency in order to save the air in the cars' Did you mean to say, "as long as the reduction rate does not exceed 3 PSI per minute..."? My understanding of drawing off air slowly to avoid triggering an emergency application is that the rate of reduction has to be under a certain amount.
SD70Dude The procedure they are describing is known as venting a train, and as long as the reduction rate exceeds 3 PSI per minute it will result in a full service brake application on the train, and a brake pipe pressure of 0 PSI. The purpose of that procedure is to not put the train in emergency in order to save the air in the cars'
The 3 PSI per minute reduction rate is required needed to trigger a car control valve to direct air from the auxiliary reservoir to the brake cylinder. A slower reduction/leakage rate may not result in any air brake application, as happened at Lac-Megantic.
The whole point of venting a train is to leave the air brakes applied (but not in emergency) and the angle cock fully open.
In my experience fully opening a angle cock when venting a train takes around a minute (actual results may vary depending on train length and how heavy a brake was already set on the train).
I can't remember offhand what the necessary reduction rate to trigger an emergency application is, but it is quite high.
SD70Dude Euclid SD70Dude The procedure they are describing is known as venting a train, and as long as the reduction rate exceeds 3 PSI per minute it will result in a full service brake application on the train, and a brake pipe pressure of 0 PSI. The purpose of that procedure is to not put the train in emergency in order to save the air in the cars' Did you mean to say, "as long as the reduction rate does not exceed 3 PSI per minute..."? My understanding of drawing off air slowly to avoid triggering an emergency application is that the rate of reduction has to be under a certain amount. The 3 PSI per minute reduction rate is required needed to trigger a car control valve to direct air from the auxiliary reservoir to the brake cylinder. A slower reduction/leakage rate may not result in any air brake application, as happened at Lac-Megantic. The whole point of venting a train is to leave the air brakes applied (but not in emergency) and the angle cock fully open. In my experience fully opening a angle cock when venting a train takes around a minute (actual results may vary depending on train length and how heavy a brake was already set on the train). I can't remember offhand what the necessary reduction rate to trigger an emergency application is, but it is quite high.
tree68 SD70Dude Cycle braking too many times can indeed achieve the same end result as Lac-Megantic, but so far all we have here is rumours, no hard facts yet. I believe a grade was mentioned, and that this was reported as a runaway. Cycle braking (and thus pssng away one's air) has been a factor in a number of runaways. Another possibility for the list.
SD70Dude Cycle braking too many times can indeed achieve the same end result as Lac-Megantic, but so far all we have here is rumours, no hard facts yet.
Johnny
SD70Dude jeffhergert It looks like the area where it happened is on a mostly 1.5 % grade. One report I was shown by a coworker said the train picked up cars (I think in Laramie WY) and was 12000 tons. One of the engines involved was a SD70m, but unknown when I was shown this info last week was if it was leading. They have a mechanical brake valve, either a 26L or the desk top equivalent, and lately some have been having pressure maintaining issues. They can have other defects where they don't work properly, but as someone has observed - you always have the "big Hole" as a last resort. Assuming the brake pressure hasn't dropped below about 45 or 50 psi. Below that pressure, emergency may not be transmitted through the brake pipe. Passenger equipment will automatically dump when pressure drops below 20 psi as a fail safe last resort. Freight equipment doesn't have that feature. Jeff Do the automatic brake valves on UP power have "freight" and "passenger" positions, or do you only have "in" and "out"? In my experience changing the automatic mode from "freight" to "passenger" (with the automatic released of course) usually makes the unit pressure maintain properly. Nearly all of CN's units with 26 and 30 type brake valves (except the ex-Oakway SD60's) have all 3 positions. We discussed this problem in another thread not so long ago, and I think it was Big Jim who said that a leaky gasket somewhere inside the control stand is the most common cause of that problem.
The SD70m engines and I think all, like the CN, with 26 or 30 type valves have freight and passenger positions. I've used passenger before because of a leaking equalizing reservoir, but many don't know about doing that. At times they seem to not want engineers running in passenger, because of the chance of accidently releasing the brake because the handle is accidently moved. Other times you'll be told to do that. I've only seen one training video that mentioned placing it in passenger, and that was after 13 years as an engineer. (I already knew about doing that, even before I went into engine service.) The engines with the brake valves cut in through the computer screens only have in/lead or out/trail options.
If it comes out that they pissed away their air then look for regulators to say we need to find a way to stop this from happening again. Train brakes work fine as long as they have AIR Pressure. However you lose the air pressure and your screwed. La Magnetic now here in the USA. The railroads are going to have to accept that the continued loss of life is unacceptable in today's society. God forbid a train did the same thing on Cajon Pass again it has happened multiple times in the past. It is time to come up with a failsafe emergency braking system for these things. Not one that if the air pressure is gone won't work one that has a mechanical backup so even if every pound of air is gone it will work. When yarding a train I understand your industry dumps all the air out of the system. When they pull the bleeder rod that could act as the catch for the spring brake to prevent the parking brakes from coming on during the switching process. What's it going to take a full tanker car full of pressurized Cholrine gas being ruptured in another derailment from a train losing air pressure for railroads to see their brakes are not up to what is needed with todays monsters.
Shadow the Cats owner If it comes out that they pissed away their air then look for regulators to say we need to find a way to stop this from happening again. Train brakes work fine as long as they have AIR Pressure. However you lose the air pressure and your screwed. La Magnetic now here in the USA. The railroads are going to have to accept that the continued loss of life is unacceptable in today's society. God forbid a train did the same thing on Cajon Pass again it has happened multiple times in the past. It is time to come up with a failsafe emergency braking system for these things. Not one that if the air pressure is gone won't work one that has a mechanical backup so even if every pound of air is gone it will work. When yarding a train I understand your industry dumps all the air out of the system. When they pull the bleeder rod that could act as the catch for the spring brake to prevent the parking brakes from coming on during the switching process. What's it going to take a full tanker car full of pressurized Cholrine gas being ruptured in another derailment from a train losing air pressure for railroads to see their brakes are not up to what is needed with todays monsters.
The prevention of peeing away the air is provided by ECP brakes.
I don't quite follow what you are saying about the bleeder rod, spring brake catch, etc. There need not be a mechanical spring brake to achieve the fail safe element that you mention.
How much do we know so far about the cause of this accident? We're discussing everything in the world based on what? I'm still waiting for us to get around to "situational awareness."
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Euclid Shadow the Cats owner If it comes out that they pissed away their air then look for regulators to say we need to find a way to stop this from happening again. Train brakes work fine as long as they have AIR Pressure. However you lose the air pressure and your screwed. La Magnetic now here in the USA. The railroads are going to have to accept that the continued loss of life is unacceptable in today's society. God forbid a train did the same thing on Cajon Pass again it has happened multiple times in the past. It is time to come up with a failsafe emergency braking system for these things. Not one that if the air pressure is gone won't work one that has a mechanical backup so even if every pound of air is gone it will work. When yarding a train I understand your industry dumps all the air out of the system. When they pull the bleeder rod that could act as the catch for the spring brake to prevent the parking brakes from coming on during the switching process. What's it going to take a full tanker car full of pressurized Cholrine gas being ruptured in another derailment from a train losing air pressure for railroads to see their brakes are not up to what is needed with todays monsters. The prevention of peeing away the air is provided by ECP brakes. I don't quite follow what you are saying about the bleeder rod, spring brake catch, etc. There need not be a mechanical spring brake to achieve the fail safe element that you mention.
Even with ECP if that fails the brakes fail back to normal airbrake functions. With a spring brake used for even emergency situations only if the brake pipeline pressure gets below a certain point then the spring overcomes the air and applies the brakes. In OTR trailers and tractors they're set to apply at 40 psi our low air warning kicks on at 60 psi. They've been mandated here for 40 year's since the 121 airbrake regulations came out.
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